install grunt-cli globally with travis for testing

.travis.yml

@@ -1,3 +1,5 @@
 language: node_js
 node_js:
   - 0.8
+before_script:
+  - npm install -g grunt-cli

package.json

@@ -25,7 +25,7 @@
     "node": ">= 0.8.0"
   },
   "scripts": {
-    "test": "./node_modules/.bin/grunt test"
+    "test": "grunt test"
   },
   "dependencies": {
     "underscore": "~1.3.3",